Natural balance active chair

ABSTRACT

A dynamic joint, to serve as part of a chair, where the dynamic joint is disposed between, and fixedly attached to, the seat and the base of the chair. The joint is operative to enable a person sitting on the chair to tilt the seat in any direction, over a substantial angle, by appropriate force from the person&#39;s pelvis and to similarly tilt the seat from any tilted position further in any direction. The Joint comprises a pair of attachment members and an elastomer body, structurally linked with them. The elastomer body is formed so as to include the tilting axes, close to the seat, and so as to control the dynamic tilting characteristics. 
     Also provided is a chair, comprising said joint, and an ergonomic seat for the chair, enabling the person to sit safely and comfortably while tilting the seat. Configuration of the chair as an exercise device is described.

This application claims priority from US Provisional Patent Applicationno. 61/381,979, filed 11 Sep. 2010, and from PCT application no.PCT/IL2011/000690, filed 29 Aug. 2011, whose disclosures areincorporated herein by reference.

TECHNICAL FIELD

The present invention relates in general to seating devices and inparticular—to tilting chairs and to fitness apparatus.

BACKGROUND ART

Accumulated sitting hours on chairs can cause health problems. Theproblems are mostly caused by technical disabilities of chairs tosupport adequate sitting postures for work in front of a desk or acomputer, and to allow comfortable and safe body movement during longsitting periods. The term chair is to be understood hereunder to includeany seating device, including a stool. With the changing industrialsociety and the increasing number of office jobs, where more employeestransacts business while sitting for long periods of time at desk and infront of computers, resultant health problems have become more common.Many past ergonomic chair designs tried to solve these problems, but thesolutions were inherently limited by technologies. Most chairs for usein offices, desk work, factories and schools, both conventional chairsand ergonomic chairs, are designed for sitting upright with a fixed90-degree angle between the upper body (also referred to herein astorso) and the thighs. Since the angle between the vertical axis of thepelvis and thighs at the hip joint can bend only 60 degrees, the rest ofthe 90 degrees bend, forced by the chair, is effected by commensuraterotation of the pelvis axis backwards, which strain the muscles of theback and causes asymmetric pressure on the inter-vertebrae discs.Therefore such a sitting posture over long periods of time may causediscomfort and back pain. In contrast a sitting position where the anglebetween the torso and the thighs is closer to 135-degrees is relaxing,allowing the spine to keep its own normal curve, what is known as‘natural lordosis’.

Thus there is a need for chairs that allow sitting at postures where thetorso-thighs angles are over 90 degrees. One solution, available in manyoffice chairs, is a back-tilting back-rest; however, the resultantposture does not allow working comfortably at a desk or in front of acomputer.

Another solution, already applied in many devices and disclosed, forexample, in U.S. Pat. No. 4,589,699 and U.S. Pat. Application2009/0284064, has the seat of the chair tilted down, relative to theground plane. If, for example the seat is tilted down by 25 degrees, andthe user's upper body is upright, the thighs will slope downward,creating an angle of 115 degrees with the upper body. Some of thedesigns of such chairs include knee rests and are therefore known as“kneeling chairs”. Sitting on such chairs for long periods is difficultsince they require much energy to maintain the upright posture, theycause pressure on the knees, as well as on the sitting bones and spine,and they are not easy to use by the common users.

The two basic solutions for the torso-thigh angle problem, discussedabove, have been shown to be unsatisfactory. They have, moreover, thedisadvantage of forcing largely fixed postures, which cause additionaldiscomfort to the user and distract from the alertness and vitalityrequired in front of a desk or a computer. Solutions are thereforedesired where the users can easily, dynamically and safely adjust thedesired torso-thighs angle, either when the body is tilted back againsta back support, or when the upper body remains upright

Rocking chairs such as disclosed in U.S. Pat. No. 4,099,697, U.S. Pat.No. 5,921,628, or other dynamic seat devices such as disclosed in U.S.Pat. No. 2009/0001788 or DE Pat. 4301734, act as rocking chairs,allowing the seat to tilt about a pivot at the base of the chair.However, since such a pivot is located far below the seat surface, theseat concurrently moves over a relatively long range, which isundesirable. Moreover, such tilting is activated mostly by the legs,creating movements of the whole body together, rather than, as is moredesirable, involving only the middle body, i.e. the pelvis and/or thelower spine and their relevant muscles. Such activation can be achievedonly if the pivot of tilting is close to the surface of the seat.

Another active dynamic chair is disclosed in U.S. Pat. No. 5,570,929.Its tilting angle and feedback pressure is a function of the user'sweight; however, its pivot is far from the seat making it difficult tomaintain balance. U.S. Pat. No. 5,590,930 discloses a tilting chair inwhich the seat has a shell shape that is placed on a bearings mechanism,tilts about a pivot above the seat and cradles the user's hips. Here themiddle body is constrained to move about a pivot more upwards the spinerather than at the lower back. Such a chair, moreover, requires the seatto have a shell form, limiting the possibility to shape it for idealsitting posture.

Another group of patents, such as U.S. Pat. No. 5,113,851 or DE Pat.19507458, disclose dynamic tilting mechanisms that allow only predefinedlimited or automated movements, rather than free movements that aredriven by the user with full flexibility and in all directions. Thesemechanisms have the additional disadvantages of being essentially heavy,large and expensive to produce and, moreover, cannot be produced asself-contained joint units, to be assembled with available seats andchair bases.

Chairs with a seat that can swing around one horizontal axis, such asare described in U.S. Pat. No. 5,261,723, allow the user to tilt theseat down, relative to the ground plane without knee support. Suchdevices are limited to tilting about one axis. Furthermore, the largesttilt angle the user can bear without siding down, or without exertingextra force, is limited, since the shape of the seat is not ideal forresisting the user from sliding down at sharp forward angles.

Other adjustable dynamic chairs, such as disclosed in U.S. Pat.application 2008/0191525 or U.S. Pat. No. 5,044,587, feature a multiaxes elastomeric joint, coupling between the seat and the base. Howeverthese joints have a carriage bolt running through the elastomer andengaging a rigid plate fixedly attached to the seat or the base. Thiscauses the mechanism to have limited tilting angles and is more suitableto function when the seat is parallel to the ground, with only momentarytilting movements. It is, moreover, not built to be tiltable indirections other than the combination of the two base axes, nor tomaintain its natural flexibility when tilted down, to allow smallmovements about a tilted position. Furthermore, it is not built towithstand constant tear forces that result from large tilt angles.

Other patent applications such as U.S. Pat. No. 2002/060486,DE102005033052 or DE202009017844, disclose seat joints with an elasticbody that buffers between rigid top and bottom plates, allowing tiltingmovements of the seat about a pivot point about two horizontal axes.However these elastomer buffers are not designed to maintain theirfunctionality under constant forward or backward tilting, or to insurelinkage of the plates to the elastomer under aggressive or repetitivetilting, or to insure long lifetime of the buffer when used for tilt.Those joints use elastomer buffering appropriate for small tilt anglesand short time durations, rather than tilting as required herein. Thefunctionality of such joints mainly relies on pressing an elastomeragainst two hard plates, so like the joint in the citations of theprevious paragraph, they may be sufficient for use in a chair where theseat remains largely parallel to ground, with occasional and relativelysmall tilting motions.

The motion limitations on the tilting joints disclosed in some of thelast citations are also due to the manner in which the elastomer isjoined to each of the plates. In the case of large, constant oraggressive tilt angles, not only shear forces are applied to the joint,but pull forces as well, since pivoting loads cause parts of theelastomer to go into tension; such pull forces, can tear the elastomeraway from the plate. Usually elastomeric buffers are subject tocompression and shear forces of vibrations, but they are not built tocope with forces caused by tilt tension, since the tensile strength ofthe elastomer and its merely adhesive links to the plates are notsufficient for long life time, or for such tilting angles. Some patentscited above may suggest an implementation wherein the elastic body ofthe joint is fixed into a corresponding penetration or recess in theplate, to secure them together, but such an arrangement is not likely tohelp much.

SUMMARY OF THE INVENTION The Technical Problem

There are technical limitations and constraints on a dynamic jointbetween the base and the seat of a chair that can fulfill the totalityof requirements as follows. The dynamic joint mechanism must allow theuser freedom to dynamically select and adjust the seat angle without anyspecial handles and controls and to do so independently from any backsupport. The same mechanism should allow the user to move the seatdynamically about any axis and from any tilt angle at which it iscurrently set, rather than only from its origin position. This mechanismshould allow the user to easily move his pelvis and lower spine, whilerelaxing the muscles of other parts of the body, in order to effectivelyrelax or strengthen the lower back. The same mechanism should allow theuser to sit for long time periods in any tilt angle that the jointenables, while supplying the appropriate feedback for the user to feelsafe and without a sensation of falling. It should, moreover, enablesubstantial, relatively large, tilt angles, relative to the ground,while keeping the joint intact, safe and reliable. ‘Substantial’, or‘substantially large’ angles, in the present context, mean tilt anglesof at least 15 degrees, preferably 45 degrees or more.

There is also a need for a complementary seat that will allow the userto tilt the seat, as well as to stay in the desired tilt angle, with noeffort to hold the body in that position or to arrest it from sliding orfalling. The latter requirement should be achieved with no physicalbarriers that may cause pressure on other parts of the body.

Any solution to the above requirements should be inexpensive, have anessentially small footprint, have a light weight and be easily adaptableto existing chairs. Dynamic joints and seats of the prior art are notcapable, nor are designed to be capable, of supporting a plurality ofthe requirements mentioned above, let alone—their totality.

Elastomer materials, which are an essential component of the dynamicjoint being disclosed herein, function in prior-art devices undercompression and vibrational shear forces only. They inherently do notwithstand tensile forces, such as may be caused by tilt in such a joint.Nor is the tensile strength of conventional adhesive links of theelastomer to metal- or other attachment members sufficient for long lifeoperation of such a joint.

Solutions to the Problem

The principle purpose of the present invention is to provide a dynamicjoint mechanism that can tilt in all directions progressively, and thatenables sitting on a chair at various postures where the torso-to-thighsangle is larger than 90 degrees—either when leaning against a backsupport, or with the upper body upright and the seat tilted forward atany angle, relative to the ground plane. This purpose is advantageouslyserved in the present invention by a dynamic seat joint that isimplemented with a flexible member, such as an elastomer or rubber, thatbuffers and links between two rigid attachment members, which areattached or attachable to the seat and the base of the chair,respectively. The flexible member is joined with each attachment memberin an interlocking structure, which ensures the integrity of the jointin face of the greatest shear- and tensile forces that may be caused byany tilting action. Preferably the elastomer is bonded to the attachmentmembers also by special glue, applied during the elastomer injectionprocess, as part of production. Preferably the elastomer is the onlymember connecting between the two metal plates, thus allowing fullflexibility of the joint movements. It can be designed with variouscompounds of the elastomer, providing various degrees of resilience, aswell as a feedback force that progressively grows as a function ofstretching length. Furthermore, the flexibility, movementcharacteristics, as well as the pivot of movement, can be controlled bydesigning the shape of the elastomer body and by the volume of theelastomer, as described here below.

Another purpose of the present invention is to provide a dynamic jointwith captive links that drastically reduce the chances that parts of thejoint will fail or disconnect from each other owing to tensile and shearforces caused dynamically or statically by large tilts. Such links wouldensure long operating life, as well as safety. A joint that serves sucha purpose should also be inexpensive to produce. This purpose isadvantageously served in the present invention by a dynamic joint thatincludes an elastomer body that meshes with the two coupling plates inthree dimensional structures, such that allow better grip between theelastomer and the plates. In one configuration, for example, structuredelements of each plate are partly buried inside the injected elastomer.In another configuration, for example, plate structures are providedthat enable tightening of the elastomer to the plates by externalforces, such as external tightening screws.

Another purpose of the present invention is to provide a dynamic jointsuch that the pivot of tilt of the joint is located below its uppersurface (which is attachable to the seat) and as close to it as desiredby the manufacturer of the chair—thus enabling user movements with theseat that are effected largely by the pelvis and the lower spinalvertebrae. This purpose is advantageously served in the presentinvention by a dynamic joint with an elastomer formed so as to have, ina vertical cross section a profile that is asymmetric along the verticalaxis, with a waist essentially high up (i.e. essentially closer to theupper surface of the joint than to its lower surface), thus creating ahigh pivot location.

Another purpose of the present invention is to provide an ergonomic seatthat may be tilted forward at essentially large angles while enablingthe user to remain sitting and arrest the user from sliding down withoutthe need for any additional support, such as a knee support. Yet anotherpurpose of the present invention is to provide a seat that distributesthe pressure evenly over the user's buttocks and allow the pelvis torest largely on the muscle tissue, instead of mostly on the sittingbones singular areas, thus to reduce pressure from the spinal cord. Boththe latter purposes are advantageously served in the present inventionby a seat with certain proposed shapes, using a combination of amoderate saddle shape with a lengthwise convex curve which lowers thethighs and a protrusion at the middle front of the seat, which may beembraced by the user with his thighs, altogether with additionalstructures, such as side portions of the seat that are raised and formsloping supporting sides, allowing the user to press his thighs towardsthem, thus increasing friction. While the dynamic joint disclosed inthis invention can be used without the ergonomic seat presented in thecurrent paragraph, wherein other types of seat can be used instead,using the seat presented here allows the user larger tilt angles withoutsliding off the seat, and supplies better load pressure distribution atany angle.

Another purpose of the present invention is to provide integrationbetween the proposed dynamic joint, the seat and the chair frame, suchthat creates a ‘natural balance’ —meaning that the user feels naturaland easy when shifting into forward or backward tilt postures, includingsuch where the angle between torso and thighs is over 90 degrees. Thispurpose is advantageously served in the present invention by the abilityto locate the proposed dynamic joint relative to the chair frame, aswell as the proposed seat relative to the dynamic joint, at the desiredbalance location, For example, if the center of mass of the seat, withthe user sitting thereon, is directly above the pivot axis of the joint,the seat will be naturally and easily balanceable by the user; if thatcenter of mass is slightly in front, or slightly back, of the pivotaxis, the seat will let the user flow naturally with the it into tiltedforward when the center of mass is at the front of the joint, or tiltedback angle when the center of mass is behind the joint. This, along withthe feedback characteristics of the joint, which are provided by theproposed elastomer shapes, will let the balancing process be controlledsafely and easily by the user, rather than forced on the user by thechair.

Another purpose of the present invention is to provide a physicalexercise device that can strengthen the inner layers of lower and upperback muscles, as well as inner layers of abdominal muscle. These musclesare otherwise ‘hard to reach’ and their strengthening is important tomaintain upright posture, as well as to prevent back pain, especially inthe lower back, damage caused to the back from long durations of staticsitting. This purpose is advantageously served in the present inventionby the proposed dynamic joint and, preferably, the ergonomic seat withthe addition of elastic straps, where those straps are connected to theframe of the chair. The straps, together with the seat and the joint,allow the chair to function as a fitness device. While tilting the seatin various directions with the pelvis, the user may use his hands orlegs to engage the elastic straps so as to create counter pressure andbalance between the different body parts. This enables exercising in acontrolled and easy manner, due to the user's ability to sit firmly andsafely while moving the upper, middle and lower body separately asdesired, while having the support of the seat, the leg control on theground and the counter pressure of the elastic straps. This exerciseability may be augmented with the addition of a swivel plate between theseat and the dynamic joint, or between the join and the frame. Thisswivel plate leverages the effectiveness of the fitness activity withthis device by integrating circular movement close to the seat surface.Together with the combination of the active joint it allows pelvismovements on the axis of the spinal cord in any tilt angle. That allowsmore body movements that mainly enhance the ability to activate thetransverse abdominals and the lower back muscles. The swivel plate canhave a free rotation, or it can have auto return functionality usinginternal compression or expansion springs. The auto return functionalitycan further enhance the effectiveness of the fitness exercises.

Another purpose of the present invention is to provide a dynamic jointthat can be mounted on top of any existing office chair mechanism, aswell as integrated with any existing or new chair design. This purposeis advantageously served in the present invention by a joint with atechnology that enables its production with a small footprint relativeto the seat and frame, as well as by its being manufacturable with anydesired mounting drill locations and any desired mounting plate size—toadapt to any chair. Alternatively it can be provided with an adaptermounting plate that will easily adapt the joint structure to fit anychair.

Another purpose of the present invention is to provide a device asproposed above with automatic capabilities to force fast or slowsmall-amplitude tilt movements of the seat in one or more axes. Suchexternally driven automatically induced vibration can reduce momentarypressure of back and body in order to relieve pain, induce blood flow,or awaken the user. This purpose is advantageously served in the presentinvention by an optional automatic vibrating, or tilting, engine thatcan be added to the proposed mechanism. Vibration engines can be added,for example, to the bottom of the seat—to induce therein small or largevibrations. Alternatively, a small motion engine can be mounted to thedynamic joint itself.

There is thus provided, according to the present invention, a dynamicjoint to serve as part of a chair, the chair including also a seat and abase, the joint being fixedly attachable to the seat and to the base,wherein the chair, when comprising the joint, is operative to enable aperson, while sitting thereon, to tilt the seat in any direction,definable in terms of two orthogonal horizontal pivot axes, over asubstantial angle by appropriate force from the person's pelvis and/orlower spine. The pivot axes of the tilting are between an upper surfaceof the joint, attachable to the seat, and a lower surface, attachable tothe base, and essentially closer to the upper surface than to the lowersurface. Preferably, the chair, when comprising the joint, is furtheroperative to enable the person, while the seat is in any tiltedposition, to dynamically tilt the seat from that position in anydirection by appropriate action of the person's pelvis and/or lowerspine.

In preferred embodiments of the invention, the joint comprises

-   -   a rigid upper member, directly or indirectly attachable to the        seat,    -   a rigid lower member, directly or indirectly attachable to the        base, and    -   a flexible member, solely disposed between the upper and lower        members and fixedly attached thereto,    -   wherein the pivot axes for all tilting movements are within the        flexible member.    -   Preferably, each of the rigid members is interlocked with the        flexible member.    -   Also preferably, the flexible member is made of at least one        elastomer and the joint is fabricated wholly by injection of one        or more of the elastomers, so as to contact the upper and lower        members.    -   Further in preferred embodiments of the invention, the structure        of the flexible member is designed to control one or more of—    -   the force required to tilt the seat in any direction,    -   the progressive variation of the force with the tilting angle        and    -   the location of the tilting pivot axes.    -   Preferably the outline shape of the flexible member is formed so        as to have a waist in at least one vertical cross-section and,        more preferably—in a plurality of vertical cross-sections, of        various azimuthal directions.    -   According to features of these configurations, the vertical        location of the waist in any vertical cross-sectional plane        determines the vertical location of the tilting pivot axis in        that plane and the outline shape affects the required force,        with respect to tilting in any direction, as a function of the        tilting angle.

In some configurations of the invention, any of the upper and lowermembers is formed so that a part thereof serves as an anchor within theflexible member, preferably formed as one or more plates, both faces ofeach plate being in contact with corresponding portions of the flexiblemember. According to a further feature, any of the plates includes oneor more holes there across, the holes being filled with an elastomerthat forms an integral part of the flexible member.

Also according to the present invention there is provided a chair,comprising:

-   -   (a) a seat,    -   (b) a base and    -   (c) a dynamic joint, directly or indirectly attached to the seat        and to the base, the chair being operative to enable a person,        while sitting thereon, to tilt the seat in any direction over a        substantial angle by appropriate force from the person's pelvis        and/or lower spine.    -   Preferably the joint is as described here above.

Also according to the present invention there is provided an ergonomicseat, to serve as part of a chair, wherein the seat is tiltable in anydirection by substantially large angles, the seat being formed so as toresist a person sitting thereon from sliding off when the seat is tiltedand so as to distribute the weight of the person essentially evenly atany tilt position or when not tilted.

Advantageous Effects of the Invention

The dynamic joint and the seat herein disclosed enable a person (theuser) to sit in any desired posture while the angle between the torsoand the thighs can be naturally set by the user to be at values above 90degrees. The user can change the angle dynamically to any othercomfortable angle, inter alia, to relieve stresses, to exercise themuscles or to allow blood flow in a body part that feels numb. The usercan achieve this by tilting the seat by any desired angle, exploitingthe capabilities of the disclosed joint and seat, with no efforts, withminimum stress and pressure and without sliding. The advantageousresults are capabilities to (a) sit and work for long time periods withimproved vitality and less pain and stress; (b) avoid accumulated bodydamage that long sitting periods may produces; (c) practice andstrengthen the muscles and the blood vessels needed to support a healthyback and a healthy body. This invention allows people to use it on anyexisting chair with very cheap adapting plate to mount the joint with.

The herein disclosed techniques for design of the joint and, possibly,of the chair allow accurate control of the location of the pivot oftilting and the characteristics of the tilting motions (such as theirprogressiveness), reduced tension on the elastomer. Proper values forsuch location and characteristics ensure stability and allow the user tosit still or to move the seat as desired. Locating the pivot as close tothe seat surface as desired enables user movements with the seat thatare derived from the pelvis and the lower vertebrae, allowing pressurerelief, better blood circulation in lower back, vitality and alertnesswhile sitting.

Progressive force feedback from the joint enables easily controlledcontinuous shift between, and combination of, fast small movements ofthe pelvis and larger body movements. It also provides stability andsafety for the user.

A technology that insures a captive linkage between the rigid attachmentmembers and the elastomer buffer, such that will not fail under staticand dynamic tensile and shear forces produced by the tilting of theseat, even if the tilting is aggressive or repetitive.

A seat with the disclosed characteristics distributes pressure evenlyover the user's buttocks and to support the person's buttocks tissue soas to allow the pelvis to rest on that tissue. It further enables theuser to sit with the seat tilted at large angles in any direction,without sliding off it and without the need for any additional support,such as a knee support.

The dynamic chair disclosed herein creates a ‘natural balance’, whereinthe user feels natural and able to easily tilt the seat forward andbackward—to achieve comfortable postures, where the angle between torsoand thighs is over 90 degrees.

The dynamic chair with added straps, disclosed herein enables a user toexercise the back and abdominal muscle so as to strengthen them, toimmunize them from back pain or to prevent damage caused to the backfrom long duration static sitting.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention is herein described, by way of example only, withreference to the accompanying drawings, wherein:

FIGS. 1A and 1B are perspective views of a chair with the dynamic jointand ergonomic seat, wherein FIG. 1A is a side view and FIG. 2B is a topfront view

FIG. 2A is a perspective view of a dynamic joint according to theinvention,

FIG. 2B is a vertical cross-sectional view of the joint of FIG. 2A in aparticular configuration.

FIGS. 2C-2F are vertical cross-sectional views of alternativeconfigurations of the joint of FIG. 2A.

FIGS. 3A and 3B are a perspective view and a vertical cross-sectionalview, respectively, of another embodiment of a dynamic joint accordingto the invention

FIG. 4 is a wire frame model drawing of one conceptual embodiment of anergonomic seat according to the invention.

FIGS. 5A and 5B illustrate, in a perspective view, attachment of thedynamic joint to the bottom of the seat at two different locations.

FIG. 6 illustrates, in corresponding multiple perspective views, varioustilt positions of the seat in the chair of FIGS. 1A and 1B.

FIGS. 7A and 7B consists of perspective views of the chair of FIGS. 1Aand 1B, with the backrest in leaned back position, wherein FIG. 7A showsthe seat in forward tilt position and FIG. 7B shows the seat in backwardtilt position.

FIG. 8 is a perspective view of exercise apparatus that comprises adynamic joint and an ergonomic seat according to the invention.

FIG. 9 is a perspective view of a swivel plate that can be mounted aboveor below the dynamic joint of the invention.

DETAILED DESCRIPTION OF EMBODIMENTS

FIGS. 1A-1B are perspective views of a chair according to an embodimentof the invention. As seen in FIG. 1A the chair is equipped with adynamic joint 101 that links between the seat 102 and a frame 103 of achair. The seat 102 is an ergonomic seat and the dynamic joint 101allows the user to tilt the seat to any side as well as forward andbackward whereas the seat 102 is an ergonomic seat that resists the userfrom sliding out of it. This chair can be equipped also with any otherchair tilt mechanism where the dynamic joint 101 can be mounted on topof such mechanism. The same structure, using the dynamic joint and theoptional seat can be applied to different frame styles and shapes, forany use.

FIGS. 2A-2F depict a dynamic joint in some embodiments of the invention,wherein FIG. 2A shows it generally in a perspective view, while FIGS.2B-2F are vertical cross-sectional views of corresponding embodiments.As seen in FIG. 2A, the joint consists of an elastomer body 201, whosehorizontal cross section has a cylindrical, oval or any polygonal shape,and upper and lower attachment members 202, made of metal or any otherrigid material. The attachment members 202 are provided with drill holes203 that allow attaching them, respectively, to the base or frame of thechair and to the seat or to a swivel plate on which the seat may bemounted. The structure of the elastomer body 201 is controlled todetermine its pivot axes and the progressive tilting characteristicswhere the feedback force, which is equal to the force that the sittingperson must exert (from his pelvis and/or lower spine) to effect thetilting, grows with the tilt angle—as explained below. In addition, thestructure of the elastomer body 201 and of attachment members 202 isjointly designed to effect strong captive coupling, between them, wherethe link of metals and elastomer will not fail and disconnect—as alsoexplained below.

FIG. 2B is vertical cross-sectional drawing of the joint in oneembodiment, as an example, depicting structural details of itscomponents. Upper plate 202 (FIG. 2A) is seen to be formed as anexternal plate 205, used for the attaching, and an internal plate, oranchor, 206, of smaller size ‘D’; the two plates are rigidly joined toeach other at a certain mutual distance ‘H3’. The plates may be made ofmetal or any other strong and rigid material. Internal plate 206 islocked inside the injected elastomer and is preferably covered withelastomer glue before the injection; it acts as a captive link to theexternal plate, and it insures that the elastomer will not fail to holdthe two attachment members together. It is used to insure better linkunder shear and tensile forces on the elastomer caused by large oraggressive tilts and adds durability and longer lifetime to the link.Anchor (inner plate) 206 can have any desired shape, such that willinterlock with the elastomer, that is—the shape of the anchor and theresultant complementary shape of the injected elastomer are such as tokeep the elastomer from slipping out from the space between the anchorand the external plate even under the most extreme shear and tensileforces caused by the tilting. A simplified preferred structure for theanchor 206 is a round plate without sharp edges and with several holesthere through, which are subsequently filled by the injectedelastomer—in permanent locking bond with the elastomer injected tobetween plates 205 and 206.

Profile outline 207 of the elastomer body includes two curves, ‘R1’ and‘R2’, shaped so as to—

(a) impart extra flexibility to the joint for small movements,(b) allow better progressive characteristics for the joint in which asthe larger the angle between the plates the larger the force needed toapply to it and the stronger the feedback force and—(c) reduce or adjust the tension within the elastomer when the joint istilted.The convergence of the curves ‘R1’ and ‘R2’ forms a circumferential‘waist’, at height ‘H2’ from the lower attachment plate.Two parameters mainly affect the tilting characteristics of thejoint—the diameter of the waist and its height H2. The waist diameter208 is shown to have different possible values, as, for example ‘D1’ to‘D4’. Each diameter value determines the amount of elastomer at thislocation when injected into the mold during joint fabrication. Differentdiameter values create different types of joints, with differentflexibility and strength. Moreover, the waist diameter may generallyvary with the azimuth of the vertical cross-sectional plane—preferablyforming a generally elliptical outline, wherein, for example, thediameter lengthwise (front-to-back) is larger than the diametercrosswise; this creates different tilt characteristics between front-and back tilts and sideways tilt. The waist outline may be furtheradjusted, to effect asymmetric tilt characteristics—for example betweenforward and backward tilts.The height ‘H2’ of the waist determines the vertical location of thepivot of tilt movement. The higher the location, the closer is the pivotto the seat, which allows faster movements. Also, the closer the pivotto the seat, the closer they are to the user's pelvis and lowervertebrae.

The vertical outline curves ‘R1’ and ‘R2’ of the elastomer within anyazimuthal plane can each be chosen to have various radius values, bothpositive and negative, to further control the characteristics of thejoint movements, such as the force required progressively for tiltingto, or the force required to tilt about, any tilt angle in that plane orin any other plane (i.e. in any direction), as a function of the tiltangle. In the configuration of FIG. 2C, for example, curve ‘R2’ 209 and‘R1’ 210 have, both, positive radii; in the configuration of FIG. 2D‘R2’ 212 is has a positive radius and ‘R1’ 211 has a negative radius; inthe configuration of FIG. 2E ‘R1’ 213 and ‘R2’ 214 have, both, negativeradii. In the configuration of FIG. 2E there is illustrated, as anexample an optional addition 215 of elastomer at the waist, to furthercontrol the tilting resilience of the structure; this feature may becombined with any other configuration, such as those discussed above, toaffect the listed tilt characteristics. In the configuration of FIG. 2Fthe curves ‘R2’ and/or ‘R1’ 216 have a radius of zero, i.e. —arestraight lines.

The term ‘waist” is to be understood, throughout, as denoting theprofile shape of the elastomer body in a vertical cross-sectional planeof any given azimuthal direction, which shape generally includes thecurves R1 and R2. Dimensional waist parameters, such as diameter orvertical location of the waist, refer to the deepest incursion points ofthe profile shape in that plane. The profile shape generally varies withthe azimuthal direction and so does the waist diameter and possibly alsoits height.

In the configuration of FIG. 2F there is also shown, by way of example,an alternative structure 217 for the implementation of the anchor(internal plates). It is constructed of several internal layers, orplates, fixed to each other and to the external plate. Such structurecan improve the linkage of the elastomer to the attachment members.

Optionally the internal plates may be covered with special adhesive thatsticks the elastomer to the metals when the elastomer is injected. Theelastomer compound can be selected for each production for extra controlof joint flexibility and characteristics; for example, the same jointshape can be produced in 40 ‘Shore A’, or 70 ‘Shore A’ hardness.

The details of the shape and composition of the elastomer body, whichmay be regarded collectively as defining its structure, have been shownhere above to control its mechanical characteristics—primarily thelocations of the tilt axes and the progressive-resistance tiltcharacteristics. The dynamic joint disclosed herein and its salientcharacteristics are therefore occasionally referred to herein as being‘structurally controlled’.

FIGS. 3A and 3B show, in perspective view and vertical sectional view,respectively, another embodiment of a dynamic joint 301 according to theinvention. It, again, includes an elastomer body, having generally acylindrical shape, preferably with a circular or elliptical crosssection, and a circumferential waist profile, which is closely linkedwith two attachment members. This embodiment is similar to that depictedin FIGS. 2A-2F in all that pertains to the elastomer body, namely thestructure (i.e. composition and form) of the elastomer that controls itstilting pivot location and its progressive tilt characteristics, as wellas the interlocking structure between it and the two attachment members.This embodiment, again, includes optional ‘H2’ and ‘H3’ parameters thatfurther define the shape and waist location of the elastomer body. Theembodiment of FIG. 3 differs, however, from that of FIG. 2 in the formand structure of the attachment members that serve to attach the joint,at one end, to the frame, or base, of the chair and at the other end—tothe seat. Here, as illustrated in FIG. 3B, each attachment member is arigid structure that includes an anchor, such as plate 304, locatedinside, and meshed with, the elastomer and a fastener, such as threadedbolt 302 (306 in FIG. 3B), or internally threaded nut 305. The anchor(e.g. internal plate 304) acts, as explained above insures that theelastomer will remain tightly joined with the two attachment members fora long time and in the face of aggressive tilting of the seat. Theinternal plate is fixedly connected with the respective fastener by anystrong bonding means known in the art, or they may be produced as asingle piece by any suitable process. Either a bolt or a nut can bedeployed independently in each attachment member as required for optimalattachment to the frame or the seat, respectively, during assembly ofthe chair. Clearly, the frame and the seat must be provided each with amatching fastener, e.g. a bolt, threaded to match the nut in the dynamicjoint, or a nut, threaded to match the bolt in the dynamic joint.Preferably the surface of the attached part of the chair that comes incontact with the corresponding face of the dynamic joint (which is theouter face of the elastomer member) is hard and flat, so that, when thecorresponding fasteners are tightened, the flat face presses theelastomer onto the internal plate, thus further strengthening the linkbetween the attachment member and the elastomer.

In an alternative configuration of the embodiment of FIG. 3, anattachment member may be provided additionally with an external metalplate, which would serve the function of holding tightly the outerelastomer layer onto the internal plate. In alternative configurationsthere may be a plurality of fasteners in each attachment member, ratherthat the single central fastener shown. It is noted that there may beother configurations of the attachment member, with similar or differentmeans of attaching or fastening to corresponding parts of the chair—allbeing within the scope of the present invention.

FIG. 4 depicts a seat that integrates the shape concepts presented inthis invention. The seat is characterized by a continuous doubly-curvedupper surface, conceptual portions of which are described as follows:401 is largely convex along the front-to-back axis and this contributesto the resistance of sliding when the seat is tilted forward, as itallow the user to lowers the thighs to form an angle larger than 90degrees between torso and thighs, while naturally shifting the center ofmass area of contact backward (toward a less inclined portion of thesurface). The convex shape contributes as well to an even pressuredistribution of the user's body on the seat. The side portions of theseat, 404, 402 and 407, are raised and form sloping supporting sides.The middle-rear side portion 402 is shaped so as to contribute to aneven pressure distribution on the user's buttocks, lifting the pelvisoff the sitting surface and to support the person's buttocks tissue toallow the pelvis to rest on those tissues, instead of mostly on thesitting bones. Portion 402 also prevents the user from sliding out fromthe seat while it is tilted sideways, thus contributing to the user'ssafety. The middle-front side portion 404 helps further to resist theuser from sliding; moreover, the user can push his thighs the legstowards outwards to press against the side surface 404, thus increasingfriction therewith to resist sliding forward. Rear side portion 407 actsas a chute that guides the user to sit at the appropriate location onthe seat, in order to achieve best fit and even pressure distribution.It also prevents the user from sliding backwards when the seat is tiledbackward.

At the middle of its back the seat has an opening 405, which allows thebuttocks to have better grip of the seat to resist sliding in a forwardtilt. It also aids in fitting different buttocks sizes to the same seatand it allows the user to freely lean back on the chair's backrest. 408is largely convex side-to-side along a cross axis, this contributes tolowering the thighs farther, as well as allowing to embrace the seat bythe thighs, to further resist sliding while the seat is in a forwardtilt. Optionally, a protrusion 403 is formed at the front of the seat,which may be embraced by the user with his thighs, to further resistsliding while the seat is in a forward tilt. The bulge 403 may have anyof many shapes, as long as it provides the same functionality,namely—being embraceable by the thighs; one of these shapes may be, forexample, a pair of protrusions—one at the inner side of each thigh.Optionally, a pair of cavities 406 are provided, located under thesitting bones so as to divert pressure off them. This is especiallyeffective when sitting upright in a forward tilt posture, when morepressure is accumulated on the sitting bones.The seat described here above is but one of many embodiments forimplementing the concepts mentioned above. The size and depth of theseat and of each portion thereof can be adjusted to fit different users,or user groups (e.g. male vs. female and old vs. young); they may alsobe adjusted to match or complement the feel and functionality of variousdynamic joints.

FIGS. 5A and 5B show, by way of example, two different relativepositions for attaching the dynamic joint to the seat. In FIG. 5A thejoint is located closer to the center of the seat 501; this will enablethe user to sit naturally balanced largely parallel to the ground, willcreate a more natural feel and movement of the seat and will enableeasier tilting backwards or sideways. In FIG. 5B the joint is locatedcloser to the back of the seat 502; this will enable the user to sitnaturally balance at a larger forward tilt of the seat. For the mostnatural feeling the attachment location should be closer to center ofweight of the user when seated. Optionally, a user-adjustable locationmechanism is provided, enabling the user to manually change, whileseated, the location of the seat relative to the joint.

FIG. 6 depicts, in multiple perspective views, a chair based on thedynamic joint mechanism and the ergonomic seat, disclosed herein, invarious tilting angles. The dynamic joint can tilt in any direction,allowing the user to set his forward or backward tilt angle of the seatas desired, or to make momentary movements to reduce pressure and induceblood flow, or to exercise the lower back and abdominal muscles in orderto strengthen them. View 601 shows the seat in a natural angle parallelto the ground, without tilting, were α1 angle is 90 degrees. View 602shows a tilted forward posture, were α2 angle is larger than 90 degreesthat can be set by the user when seated. View 603 shows a steeper angleof forward tilting than the previous view, were α3 angle is larger thanα2. View 604 shows a backward tilt position, were α1 angle is smallerthan 90 degrees, which can be used, for example, when leaning back ontothe backrest. View 605 shows a side tilt position, were β1 is an anglein an orthogonal axis to α and is smaller than 90 degrees. View 606shows a combination of side and front tilt position, were β2 angle issmaller than 90 degrees and α is larger than 90 degrees. The user canforce the seat to tilt in any direction—allowing him the ability to drawmovements like circle tilting or any kinds of movement desired torelieve pain or to train his muscles. This chair can be equipped withany other components, such as back cushion, armrest, or various frameshapes of any material.

FIGS. 7A and 7B depict a chair that uses the dynamic joint as aleaning-back tilt mechanism to enable a user to easily lean onto thebackrest. The dynamic joint can replace any tilting mechanisms thatexist in chairs, or it can be mounted on top of any existing mechanismto further improve sitting postures. FIG. 7A shows a leaned-back posturewhere the seat is tilted forward, allowing the user to lean back in anopen posture, where the body is stretched out. FIG. 7B shows aleaned-back posture where the seat is tilted backward, allowing the userto lean back in a ‘cradled’ posture.

FIG. 8 depicts a chair according to the invention, configured as afitness, or exercise, apparatus. This chair comprises a dynamic jointand, preferably, an ergonomic seat with all the capabilities explainedabove and may as well be equipped with a backrest (not shown). It isgenerally equipped with any of a variety of auxiliary parts, such asstraps, elastic straps, bars or handles. In the configuration shown, thechair is equipped with elastic straps 801, which can be made ofelastomer, or any other flexible material. The elastic straps 801 areattached, for example, to end-points 802 on the base of the chair; anytype of base or frame, aside from that shown, can be used for the chairand the mounting locations can be changed. Optional handles 803 areprovided for the user to easily hold the elastic straps and stretch themwhile exercising. The user can sit on the chair and hold the elasticstraps by his hands, or other parts of the body, while the elasticstraps act as counter force to any of the user's movements, which aredone with the aid of the tilting seat—thus allowing furtherstrengthening of the muscles that are activated by the movement. Theelastic straps may be of various types and have various values ofstrength and length, so as to adjust the load and force of the straps.With a specific set of exercises, the user can use this fitnessapparatus to easily strengthen his lower back muscles and innerabdominal muscles, so as to be able to hold his back straight, to reducepain and to immunize the lower back from injuries due to back healthproblems. Some possible exercises, performed while seated on the fitnessapparatus, include, for example, pushing the seat to the left with theright leg while pushing/stretching the elastic band with the right handin a counter direction; or pushing/stretching the straps with the handsupward while tilting the seat in any direction; or rotating the seat; orcrossing hands close to the body and forcing the seat to tilt or turnwith the pelvis. It is possible to connect additional elastic straps toother parts of the chair's frame, in order to provide counter force tomovements in several different directions.

FIG. 9 shows a swivel plate that can be mounted between the dynamicjoint and the seat, or between the frame and the dynamic joint. It canbe any standard swivel plate produced as a generic product and availablein the markets. It generally comprises a bottom metal plate 901, and anupper metal plate 902, connected to each other by a rotational bearing903. Either or both of the plates may optionally be provided withmounting holes 904. Such a swivel plate allows the seat to have circularrotations movement around the vertical axes at any tilted position ofthe dynamic joint. Integrating circular movement close to the seatsurface with the tilting of the dynamic joint enables pelvis movementson the axis of the spinal cord in any tilt angle. Such functionalityallows additional body movements and enhances the ability to activatethe deeper muscles of the back and the abdomen.

INDUSTRIAL APPLICABILITY

The dynamic joint and ergonomic seat presented in this invention can beassembled to any chair or frame. For example, any chair that is builtwith any off the shelf mechanisms and ensembles can be equipped with theherein-presented joint, and optionally with the herein-presented seat.The joint and the seat can also be integrated into any new design of achair. The chair can be of any type, such as an office chair, a schoolchair, a bar stool, etc. The greatest benefits are for chairs that areused for work in front of a desk or a computer, but also any other typeof chair may benefit.

The joint can be attached to any existing chair by a simple adapterplate, using any fastening means.

The ergonomic seat presented here can replace the seat of an existingchair—to allow better pressure distribution on the seat. It can as wellbe integrated with the presented dynamic joint, allowing effortless andeasy dynamic movements and extended possible sitting postures for workor comfort.

The dynamic joint and ergonomic seat presented in this invention, withadditional elastic straps mounted to a chair's frame, can perform as afitness apparatus. The elastic straps together with the dynamic jointallow the chair to act as a fitness device. Moving the seat with thepelvis while the hands or legs use the elastic straps to create counterpressure between the different body parts. Such fitness apparatus can beused indoor or outdoor and can strengthen all body muscles, with specialcapabilities to strengthen back and inner abdominal muscles to supportstrong and healthy back. The dynamic joint and, optionally, theergonomic seat presented herein can be assembled to any fitnessequipment, existing or under design or fabrication, replacing theconventional seat therein. This would allow the user to sit in postureswith less stress on the spine and cartilages, as well as to improve hiscapabilities to activate more muscles while practicing.

The joint disclosed herein can be easily produced by any elastomerinjection process, or vulcanization process. Due to the innovativedesign disclosed here, a wide variety of elastomer compounds, as well asvariety of adhesives between elastomer and plates members, can be used,enabling the required functionality at low production costs.

The seat disclosed herein can be produced with various types ofmaterials and by various fabrication processes, such that will allow itto maintain its shape under the pressure of human weight and thepressure created by the mounting joint feedback when tilted. Suchmaterials and processes are well known in the art.

1. A dynamic joint serving as part of a chair, the chair including aseat and a base, the joint being attachable to the seat and to the baseand comprising: a rigid upper member, directly or indirectly attachableto the seat; a rigid lower member, directly or indirectly attachable tothe base; and a single flexible member, solely disposed between saidupper and lower members and fixedly attached thereto, wherein said uppermember is tiltable with respect to said lower member over a substantialtilt angle about a horizontal pivot axis locatable below the uppermember and above the lower member.
 2. The joint as in claim 1, whereinsaid tilting is variable in at least one direction, said pivot axisdefinable by two orthogonal horizontal axes.
 3. The joint as in claim 2,wherein the direction of said tilting is dynamically varied. 4.(canceled)
 5. The joint as in claim 3, wherein said flexible member ismade of at least one elastomer and contacts said upper and lowermembers.
 6. The joint as in claim 3, wherein any of said rigid membersis formed to interlock with said flexible member.
 7. The joint as inclaim 3, wherein the structure of said flexible member is configured toaffect, with respect to any tilting direction, one or more of— a forcerequired to tilt said upper member, a progressive variation of saidforce with the tilting angle and a vertical location of said pivot axis.8. The joint as in claim 3, wherein said flexible member has a singlecircumferential surface, defining a waist, which has a diameter, in atleast one vertical cross-section, and said surface further formed tohave said waist positionable in a plurality of vertical cross-sectionsof a plurality of azimuthal directions.
 9. (canceled)
 10. The joint asin claim 8, wherein said diameter is generally variable with theazimuthal direction and said waist has a vertical location in a verticalcross-sectional plane, said vertical location defining a verticalposition of the pivot axis when said joint is tiltable in the respectivevertical cross-sectional plane, and said waist configurable in anyvertical cross-sectional plane to affect a force required to tilt saidupper member as a function of said tilt angle.
 11. (canceled) 12.(canceled)
 13. The joint as in claim 3, wherein at least one of saidrigid members is further formed so that a part thereof serves as ananchor within said flexible member.
 14. The joint as in claim 13,wherein said part that is formable as at least one plate having at leastone face contacting corresponding portions of said flexible member. 15.The joint as in claim 14, wherein at least one of said plates includesat least one hole therein, the at least one hole fillable with anelastomer forming an integral part of said flexible member. 16.(canceled)
 17. (canceled)
 18. (canceled)
 19. (canceled)
 20. (canceled)21. (canceled)
 22. (canceled)
 23. (canceled)
 24. (canceled) 25.(canceled)
 26. An ergonomic seat, adapted to serve as part of a chair,wherein the seat is tiltable in at least one direction by a substantialtilt angle, the seat formable to arrest a person sitting thereon fromsliding thereoff when the seat is tilted and to distribute the weight ofthe person substantially evenly when the seat is tilted and when nottilted.
 27. (canceled)
 28. (canceled)
 29. (canceled)
 30. (canceled) 31.(canceled)
 32. (canceled)
 33. (canceled)
 34. (canceled)